The present invention is directed to a method and to a manually manipulatable, gyro-stabilized indicating apparatus for practicing the method by which pipefitters, carpenters, builders, land and road graders and the like may solve construction problems involving determining in space the known or unknown orientations of structures, road grades and the like with reference to fixed or desired known or unknown orientations.
A carpenter's or builder's level or instrument usually has one or more bubble devices mounted in a longitudinal member having at least one flat surface for determining by gravity whether or not a surface is on an even horizontal plane or for adjusting a surface to such plane. It may also be used to determine whether or not an upright surface is "in plumb" or at 90.degree. or at a right angle with respect to a horizontal surface. The bubble device may be a glass or clear plastic tube partly filled with ether or alcohol or other suitable medium so as to leave an air bubble that moves to the exact center of the tube when an instrument, for instance, is on an even horizontal plane. This instrument, however, cannot be used to determine a desired angular orientation of a surface within a horizontal plane.
For example, in constructing and welding together pipelines where it is desired to construct laterals, which may be branch lines extending from the main line at less than 90.degree.; tees, which are lines extending at right angles; elbows, which extend usually at 90.degree. and 45.degree., elaborate pre-constructed jigs may be used to hold the structures at the desired angle for welding. Conventional carpenter's or builder's levels with one or more bubble devices have also been used by rotating or turning over the entire pipe structure until it is positioned in a manner that such instrument may be used to determine an angle that otherwise in the normal erected position would be within a horizontal plane. This, however, is a cumbersome procedure and can become quite awkward if not impossible in some situations.
In putting together larger structures, such as structural frames for buildings, a surveyor's transit instrument may be used in some instances.
Gyroscopes are well known in the art. Their spinning wheels tend to "remember" their position in space, following the law that a rotating mass will keep turning about its axis (the imaginary line around which it revolves) unless acted upon by some angular torque, i.e., a single force that produces a twisting rotation. In other words, a spinning mass wants only to keep spinning forever in the same way, at the same speed, on the same axis (assuming, of course, air and bearing friction did not act to slow it down and eventually stop it). As long as the rotating mass or spinning wheel continues to spin or rotate, the axle of the wheel tends to remain pointing at a fixed spot in space unless an outside force shifts it. "Gyroscopic inertia" is that property of a gyroscope which causes it to maintain the direction of the spin axis in space provided that any force acting on it does not cause a torque around any axis other than the spin axis. "Precession" is the response of a rotating mass or spinning wheel to any force tending to change the position of its spin axis. It is the turning movement of the gyroscope in space occurring when a force acts on it in such a way as to cause a torque around any axis other than the spin axis. A simple top turning clockwise, for instance, is an example of a rotating mass. If without slowing its rotation, a tilt force can be applied in a northerly direction (in other words, a direction away from the person applying the force), instead of heeling over toward the north, the top will tilt to the right or eastward. It thus has precessed; i.e., turned the effort around a corner or 90 degrees from its original direction. If the tilt effort were in a southerly direction, the top would precess to the west. If the top were turning counterclockwise, the direction of precession for each tilting force would be reversed from that described above. If the top were changed to a wheel and placed in a frame, the northerly-applied tilt is really a torque around the west-east axis, while precession occurs around the north-south axis. Precession, therefore, makes the spin axis tend to align itself with the torque axis; i.e., not with the direction of one's push, but rather with the axis around which the push is applied, which is 90 degrees around.
Gyros may be mounted so that they have a single pair of gimbal bearings for tilting freely about one axis (called "a single-degree-of-freedom gyro"). The gimbal can rotate freely around an "output axis" perpendicular to the axis of the wheel's spin. If mounted in an aircraft, any turning motion of the aircraft around the "input axis" (for example, a turn of the horizontal heading) produces a torque about the output axis that counteracts this motion and thus holds the gyroscope platform in a stable position.
If a gyro gimbal is mounted in a second ring or frame (gimbal) on suitable bearings, it is called a "two-degree-of-freedom gyro".
Gyros have been and are employed for many applications, including providing an artificial horizon aboard ships for taking sextant readings; serving as part of a torpedo steering mechanism; serving to stabilize and reduce the degree of roll of a ship; used in guidance systems for space vehicles; used in airplanes to indicate the altitude of an airplane at any moment and through a full 360 degrees of roll and pitch; as part of a compass for ships; as part of an automatic pilot to hold an aircraft in straight and level flight, to mention only a few uses. Gyros also serve as part of an apparatus for surveying base holes for oil wells and the like, such as described in U.S. Pat. No. 2,857,677.
The purpose of my invention is to provide an instrument, somewhat similar to the well-known carpenter's level, but employing a gyro arrangement by which horizontal degrees roll, and vertical pitch may be determined from a single instrument that in use is intended to be manually manipulatable by the operator to solve problems in construction, piping, road grading, and the like. As previously mentioned above, a carpenter's level with bubble devices cannot determine angles within a horizontal plane. My invention may be coupled with bubble devices, if desired, but a single gyro suitably mounted to give an indication of degrees within a horizontal plane while a bubble device gives to a limited extent both indications of roll and vertical pitch; or a pair of gyros, one giving the horizontal degrees and the other giving roll and vertical pitch; or three gyros, one giving horizontal degrees, a second giving degrees of roll and a third giving the degrees of vertical pitch; these will enable one to make the various angular determinations discussed herein.
In the instance of the pair of gyros mentioned above, or in the instance of the three gyros also mentioned above, these may be used without bubble devices, but the inclusion of a bubble device may be additionally preferred for orientation of the instrument with the earth.